A slide fastener is a tool for opening and closing an article used in familiar daily necessities such as clothes, bags, shoes and miscellaneous goods, as well as industrial goods such as water storage tanks, fishing nets and space suites. The slide fastener is mainly comprised of three parts: a pair of long fastener tapes, a number of elements which are engaging portions of the fastener and are attached along one side edge of each tape, and a slider for controlling opening and closing of the fastener by engaging or separating the elements opposed to each other.
One of methods for attaching the elements to the fastener tape is injection molding of a synthetic resin to a core portion formed on one side edge of the fastener tape. A polyacetal (polyoxymethylene) resin is known as a material for forming the elements (Japanese Patent Application Public Disclosure (KOKAI) No. 2007-021023 A1). The polyacetal resin is an engineering resin having good balance between strength, elasticity, a creep property, impact resistance and a cyclic fatigue property, and is widely used in various mechanical parts as well as OA equipment.
In addition, Japanese Patent Application Public Disclosure (KOKAI) No. H05-125256 and WO 01/032775 disclose that the polyacetal resin can be used as a fastener material, and a glass fiber may be also added as a reinforcing agent or an inorganic filler. Further, WO 01/032775 discloses that the inorganic filler is preferably in the range of 0.5 to 100 parts by weight, and more preferably in the range of 2 to 80 parts by weight based on 100 parts by weight of the polyoxymethylene resin, and that the amount of less than 0.5 part by weight of the inorganic filler is insufficient for the reinforcing effect of the filler, and the amount of more than 100 parts leads to deterioration of the surface appearance and a decrease in molding formability and impact resistance, which are not preferred.